Brake pressure booster

Abstract

A brake pressure booster for a vehicle brake system comprises a vacuum booster which includes two chambers, the low pressure chamber (16) of which is evacuated during actuation in a brake pressure boosting fashion, while a pressure higher than that in the low pressure chamber is adjustable in the high pressure chamber (14) by means of a control valve (28), the higher pressure exceeding the external atmospheric pressure. That is accomplished by a mechanical regulating valve (12) connected upstream of the control valve (28). Upon connection of a pressure source (18) to the high pressure chamber (14), a valve seat controlling access from the pressure source (18) to the valve opens before another valve seat closes that controls the connection between an inlet (24) into the valve and the high pressure chamber (14).

What is claimed is: 
     
       1. A brake pressure booster for a vehicle brake system, comprising a vacuum booster (10) which comprises two chambers (14, 16), the low pressure chamber (16) of which is evacuated during actuation in a brake pressure boosting fashion, while a pressure higher than that in the low pressure chamber (16) is adjustable in the high pressure chamber (14) by means of a control valve (28), the higher pressure corresponding at least to the external atmospheric pressure,   a valve (12) disposed upstream of the control valve (28), with respect to the vacuum booster (10), to establish communication between the high pressure chamber (14) and a pressure source (18) when atmospheric pressure is reached in the high pressure chamber (14), the pressure source (18) generating pressure higher than atmospheric pressure in the high pressure chamber (14),   the valve (12) having a first inlet (22) for air at atmospheric pressure and a second inlet (24) for air whose pressure corresponds to that in the high pressure chamber (14), the air pressure differential between the first and second inlets (22, 24) opening the valve (12) for establishment of the connection between the pressure source (18) and the high pressure chamber (14) when atmospheric pressure has been reached in the high pressure chamber (14), characterized in that a valve seat (38) controlling access from the pressure source (18) to the valve (12) opens before a valve seat (42) controlling a connection from the second inlet (24) to the high pressure chamber (14) opens, while a valve seat (40) controlling a connection from the pressure source (18) to the high pressure chamber (14) still remains closed, as communication is established between the pressure source (18) and the high pressure chamber (14).